Regular Expressions 101

Positive Lookahead(?=(?'a'[\s\S]*))

Group a(?'a'[\s\S]*)

Character Class[\s\S]*

*matches any number of characters from the set below:

\sany whitespace character

\Sany non-whitespace character

Group b(?'b'X(?=\k'a'\z)|(?<=(?=x^|(?&b))[\s\S]))

1st AlternativeX(?=\k'a'\z)

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive)

Positive Lookahead(?=\k'a'\z)

\k'a'the text saved by group a

\zend of string

2nd Alternative(?<=(?=x^|(?&b))[\s\S])

Positive Lookbehind(?<=(?=x^|(?&b))[\s\S])

Positive Lookahead(?=x^|(?&b))

1st Alternativex^

xthe literal x (120₁₀ / 170₈ / 78₁₆) (case sensitive)

^start of string

2nd Alternative(?&b)

(?&b)calls group b as a subroutine

Character Class[\s\S]

\sany whitespace character

\Sany non-whitespace character

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?=(?'a'[\s\S]*))(?'b'X(?=\k'a'\z)|(?<=(?=x^|(?&b))[\s\S]))

New

bla X bla